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  • #139387
    Streen
    Participant

    This is something that I’ve been pondering for a long time now, and I never really had the chance to ask a science teacher this, but maybe someone here knows the answer.

    Okay… I understand that we see color because that is the wave frequency (or some such) that is being bounced off the object we’re looking at.  But what makes one thing reflect one color and another object reflect a different color?  What is fundamentally different about the two objects that causes it?

    #150807
    Jax
    Keymaster

    Color science is interesting and more complex than we think (yet also fairly simple it seems as well).  I found this interesting little thing, Ask a Color Scientist, that you’ll have fun with I suspect. http://www.cis.rit.edu/mcsl/outreach/faq.php?catnum=6#856

    Here is an overview of color: http://www.webexhibits.org/causesofcolor/index.html  It’s written for the non-scientist, and as such they don’t use as many scientific words – they say color made (instead of radiated) color lost (instead of absorbed), it’s kind of grating.  lol  But, other than that it seems to be a pretty good overview.  You might find it interesting.

    That should get you a start.  I don’t know too much about color, as it’s rarely covered in depth in classes, but I also find it interesting.  Hopefully this helps.

    #150818
    Kol Drake
    Moderator

         In order to understand the colors of objects, one must first appreciate something about the nature of visible light. Since light acts as a wave, it may be characterized by its wavelength, ranging from about 400 nanometers for violet light (where one nanometer equals one billionth of a meter), to about 700 nanometers for red light. The other colors of visible light, and their wavelengths in nanometers, are blue (470), green (530), yellow (580), and orange (620). The energy of light depends upon its wavelength; shorter wavelengths have higher energies than longer wavelengths.

         The light produced by most lamps, and by the sun, contains all visible colors, and is perceived as white. When an object is illuminated by white light, it may be reflected, transmitted, or absorbed. It is the wavelengths of the reflected and transmitted light that determine the color that we perceive. For example, the leaves of most plants absorb red and blue light very strongly and reflect green light efficiently. Carrots, on the other hand, absorb blue and green light and reflect yellow, orange and red light. So we perceive leaves to be green and carrots as orange. The exact shades of the colors that we observe depend upon the precise wavelengths that are absorbed. Smooth and rough surfaces reflect light differently, making some objects appear shiny and others dull.

         Most objects are made up of molecules, which in turn consist of individual atoms held together by electrons. It is the electrons in atoms and molecules that are responsible for the absorption of light. For example, when the molecule chlorophyll in plants absorbs blue or red light, an electron is excited from a low energy state to a higher energy state. The energy difference between the two states must be exactly equal to the energy of the absorbed light. In the case of chlorophyll, the energy gaps between the lower and higher energy states correspond to light that appears either red or blue to our eye, and the unabsorbed green light is reflected. On the other hand, the energy of light absorbed by electrons in carotene, the molecule responsible for the color of carrots, corresponds to wavelengths perceived as blue and green, and orange and red light is reflected. The carbon in charcoal or in a pencil absorbs all visible colors. Very little visible light is reflected, so these materials appear black. White paper and white cloth do not absorb visible wavelengths, but instead reflect all of them.

         So, The color of the objects which we see are largely due to the way those objects interact with light and ultimately reflect or transmit it to our eyes. The color of an object is not actually within the object itself. Rather, the color is in the light which shines upon it and is ultimately reflected or transmitted to our eyes.

         The role that the object plays is that it might contain atoms capable of selectively absorbing one or more frequencies of the visible light which shine upon it.

    #150819
    Beral Khan
    Participant

    This lends itself to my thoughts on communication between objects both inanimate and animate. Visual communication through the use of color could be interesting to explore.

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